In recent years, organic light emitting devices represented by an organic electroluminescent light emitting device are attracting attention as display or lighting technique, and studies for the practical use thereof are actively under way. In particular, enhancing the light emission efficiency is an important study subject, and currently, phosphorescent materials which use light emission from excited triplet state are attracting attention as a light emitting material.
When light emission from excited singlet state is used, the probability of generation of the light emitting excitons is believed to be 25% since the singlet excitons and triplet excitons are generated at a ratio of 1:3. Furthermore, since the light extraction efficiency is approximately 20%, limit of the external extraction quantum efficiency is believed to be 5%. On the other hand, if an excited triplet state is also used, the upper limit of internal quantum efficiency is 100%, and thus, in principle, the light emission efficiency becomes 4 times larger than that in the case of an excited singlet state. Under this background, intensive studies for development of a phosphorescent material for organic light emitting device are actively under progress. For example, as a phosphorescent material, an iridium complex which has a 2-phenylpyrimidine ligand is disclosed (see, Patent Literature 1, for example). Furthermore, a 2-phenylpyrimidine based iridium complex which has excellent solubility and is suitable for coating process is disclosed (see, Patent Literature 2, for example).